JP2866131B2 - Method for producing ultrafine long-fiber nonwoven fabric - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a nonwoven fabric made of ultrafine fibers, and more particularly, to a method for producing a nonwoven fabric made of ultrafine fibers having a delicate surface morphology and a dense structure. It relates to a manufacturing method.

(Prior Art) Conventionally, nonwoven fabrics have been used for various purposes such as clothing, industrial materials, civil engineering and building materials, agricultural and entertainment materials, living related materials and medical hygiene materials. In particular, nonwoven fabrics made of long fibers are more
It is widely used because of its high strength and excellent productivity. Many attempts have been made to obtain a nonwoven fabric having a delicate surface and a dense structure in the nonwoven fabric made of long fibers. For example, Japanese Patent Publication No. 44-24699, Japanese Patent Publication No. 52-30629 and Japanese Patent Publication No.
A method is disclosed in which a sheet is subjected to a chemical treatment to dissolve a part of the polymer constituting the fiber, or is dissolved and removed to obtain a nonwoven fabric composed of fine fibers. Further, Japanese Patent Publication Nos. 1-47585 and 1-47586 disclose that a sheet is treated with a high-pressure water stream to split the fibers into ultrafine fibers, and that the fibers are three-dimensionally entangled. A method for obtaining a nonwoven fabric comprising ultrafine fibers is disclosed in Japanese Patent Publication No. 47579/1994, in which the nonwoven fabric is washed with water to remove water-soluble components. However, these nonwoven fabric manufacturing methods have a problem that the production process is complicated and the production cost is high because the polymer must be removed. further,
Japanese Patent Publication No. 53-10169 discloses a method of obtaining a nonwoven fabric made of ultrafine fibers by buffing a sheet and splitting the fibers. There is a problem of being damaged.

(Problems to be Solved by the Invention) The present invention is intended to solve the above-mentioned problems and to provide a method capable of efficiently producing a nonwoven fabric composed of ultrafine long fibers having a delicate surface morphology and a dense structure. It is.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the present inventors have reached the present invention. That is, the present invention relates to a polymer component A and two or more polymer components B which are incompatible with the polymer component A and have a melting point higher by 30 to 150 ° C. than the melting point of the polymer component A. And a segment having a convex lens-shaped cross-section, and a radius of curvature at the convex lens-shaped portion due to the polymer component B in a cross-section perpendicular to the fiber axis.
R ₀ and R ₁ , and the arc lengths L ₀ and L ₁ of the circular arc satisfy the following formula and melt-spun bicomponent conjugate filaments, and the spun split bicomponent conjugate filaments are drawn by air suction. The high-melting-point polymer component B is collected by taking up by a picking means, depositing it on a collecting surface of a web conveyor or the like to form a web, and treating the web with a group of high linear pressure rolls composed of two or more rolls. At least partially exfoliating the composite fiber from the composite filament to obtain a split filament, and at least partially bonding the fibers with the fiber comprising the polymer component A having a low melting point. Of the present invention.

R ₁ / R ₀ <1 ... 1 <L ₁ / L ₀ ≤3 ... [R ₀ : radius of curvature of an arc not in contact with polymer component A, R ₁ :
Radius of curvature of an arc in contact with polymer component A, L ₀ : arc length of an arc not in contact with polymer component A, L ₁ : arc length of an arc in contact with polymer component A] Will be described in detail.

The incompatible polymer components A and B referred to in the present invention both have fiber-forming ability and can be melt-spun using a conventional melt-spinning apparatus. Polymer component A
And B are, for example, polyester-based and polyamide-based, polyester-based and polyolefin-based, polyamide-based and polyolefin-based, and the like. As the polyester-based polymer, polyethylene terephthalate, polybutylene terephthalate or a mixture of these as a main component is used. Polyesters such as nylons, polyamides such as nylon 6, nylon 46, nylon 66, nylon 610, or polyamides such as copolymerized nylon based on them. Polyolefins such as polypropylene and high density polyethylene And polyolefins such as linear low-density polyethylene and ethylene / propylene copolymer. The polymer components A and B have
Additives such as ordinary matting agents, heat stabilizers, pigments or crystallization accelerators for polymers may be added.

The method for producing the ultrafine long-fiber nonwoven fabric according to the present invention comprises the steps of: first, the polymer component A is incompatible with the polymer component A;
And two or more segments having a convex lens-like cross section composed of a polymer component B having a melting point higher by 30 to 150 ° C. than the melting point of the polymer component A. The composite spinning is performed using a spinning apparatus. As the spinneret device, a composite spinneret device having a structure in which two or more molten polymer components B are guided from the outer periphery of the introduction hole of the molten polymer component A is used. The number by which the polymer component A divides the polymer component B, that is, the number of the segments having the convex lens-like cross section made of the polymer component B is preferably 2 or more, and the larger the number, the more preferable the fine fiber can be obtained. If the amount is too large, the cross-sectional structure in which the segments composed only of the polymer component B are bonded to each other will cause a problem that splitting and peeling cannot be performed in a later process. Good. Further, the segment composed of the polymer component B needs to have a convex lens-shaped cross section.
Since the contact circumference in which the segment consisting of only the polymer component A comes into contact with the polymer component A is relatively short, the splitting property is improved when splitting the bicomponent composite filament in the subsequent step.

Next, the spun bicomponent bicomponent fiber is taken out by a take-up means such as an air sucker and deposited on a collecting surface of a web conveyor or the like, and the web is heated by a group of rolls heated at a high linear pressure and having a smooth surface. By the treatment, the segment composed of the high melting point polymer component B is peeled from the composite long fiber to obtain split long fibers, and at the same time, the fibers are bonded at least partially by the fiber composed of the low melting point polymer component A. I do.
Further, the web is treated with a group of non-heated surface smooth rolls of high linear pressure, and the segment composed of the high melting point polymer component B is once separated from the composite filaments to obtain split filaments. The fibers may be at least partially adhered to each other with fibers made of the polymer component A having a low melting point. A heated embossing roll can be used instead of a heating roll having a smooth surface. Using a heated web with an embossing roll, the fibers are at least partially adhered to each other with fibers of a low melting point polymer component A to obtain a nonwoven fabric.
Next, the segment composed of the polymer component B having a high melting point may be peeled off from the composite filament by treating the nonwoven fabric with a group of rolls having a smooth surface at a high linear pressure to obtain split filaments. The obtained nonwoven fabric may be subjected to a softening process for improving the flexibility of the nonwoven fabric.

The polymer component B according to the present invention needs to have a melting point 30 to 150 ° C. higher than the melting point of the polymer component A. The melting point of the polymer referred to in the present invention is determined by using a DSC-2 type differential calorimeter manufactured by Perkin Elmer Co. according to the manual of the apparatus.
It was determined from a DSC curve obtained by measuring the sample amount at about 5 mg and the scanning speed at 20 ° C./min. If the difference between the melting points of the polymer component B and the polymer component A is less than 30 ° C., when the web is heat-bonded with a heating roll, the nonwoven fabric is thermally contracted, the dimensional stability is reduced, and the hand of the nonwoven fabric is deteriorated. It is not preferable because there are problems such as that the temperature range becomes narrow and the temperature control becomes difficult during thermal bonding. If the melting point difference exceeds 150 ° C., thermal degradation of the low melting point polymer component A is promoted, which is not preferable. When the web is thermally bonded with a heating roll having a surface temperature equal to or higher than the melting point of the low melting polymer component A,
The resulting nonwoven fabric is not preferred because it has a film shape or a hard surface.

For web formation, drawn filaments obtained by cooling and drawing a melt-spun fiber bundle or highly oriented undrawn filaments obtained by a high-speed spinning method can be used. The process from spinning to web formation may be a continuous process, or the web may be made from a separately manufactured drawn long fiber or a highly oriented undrawn long fiber. The web is created by taking up these long fibers with a take-up means such as an air sucker, forcibly charging with a charging device, opening the fibers, and depositing the fibers on a collecting surface of a moving web conveyor or the like. .

The high linear pressure roll group referred to in the present invention is composed of two or more rolls. Generally, from a pair of rolls to a multistage type of a total of ten rolls can be used. If the number of rolls is too large, capital investment costs increase, which is not preferable. The linear pressure of the roll group is an important factor in separating the segment composed of the polymer component B having a high melting point from the composite filament and forming a split filament, and the stress such as shearing, elongation, or compression causes the polymer to lose its length. The segment consisting of component B is peeled off.
Although this linear pressure depends on the splitting property of the composite filament,
It is preferably at least about 20 kg / cm. If it is less than 20 kg / cm, the segment comprising the polymer component B cannot be sufficiently peeled off, which is not preferable.

Next, the bicomponent composite long fiber according to the present invention will be described.

FIG. 1 is a cross-sectional view for explaining the structure of the bicomponent conjugate filament according to the present invention, and FIGS. 2, 3, 4 and 5 show the bicomponent conjugate filaments satisfying the constitutional requirements of the present invention. It is a cross section showing an example. In FIG. 1, R ₀ and R ₁ are the radii of curvature at the convex lens-like portions due to the polymer component B in the cross section perpendicular to the fiber axis of the bicomponent bicomponent fiber, and R ₀ is the polymer component A.
The radius of curvature of the arc not in contact with the polymer component A, R ₁ is the radius of curvature of the arc in contact with the polymer component A, L ₀ and L ₁ are the arc lengths of the arc in the convex lens-like portion, and L ₀ is the polymer component arc length of the arc that is not in contact with a, L ₁ is the arc length of the arc that is in contact with the polymer components a. R ₀ and R ₁ are 90% of the arc length of each circular arc based on the cross-sectional photograph taken by magnifying the fiber cross section 1000 times.
The above is obtained by assuming a virtual arc that includes the above. L ₀ and L ₁ were obtained by actual measurement from the enlarged cross-sectional photograph.

The bicomponent bicomponent fiber according to the present invention has the R ₀ shown in FIG.
And R ₁ , L ₀ and L ₁ satisfy the following and formulas.

R ₁ / R ₀ <1 ... 1 <L ₁ / L ₀ ≤3 ... If this R ₁ / R ₀ is R ₁ / R ₀ ≥1, L ₁ / L ₀ naturally becomes L ₁ / L ₀ ≤
However, in this case, depending on the selected polymer component A and polymer component B, the polymer component A and the polymer component B are separated in the spinning step or the drawing step, and the spinning step or the drawing step is performed. Inconveniences such as thread breakage occur in the process, and when the web is formed, the fiber opening property is reduced and a uniform web cannot be obtained, which is not preferable. If R ₁ / R ₀ satisfies R ₁ / R ₀ ≧ 1, L ₁ / L ₀ naturally becomes 1 <L ₁ / L _{0. In} this case,
Depending on the polymer component A and the polymer component B to be selected, the polymer component A and the polymer component B are used in the spinning step or the drawing step.
Is not peeled off, and a uniform web with good fiber opening properties can be obtained when the web is formed. However, R ₁ / R ₀ is _{R 1 / R 0 <L 1} / L 0 be a 1 L ₁ / L _0> 3
In this case, it is difficult to separate the polymer component A and the polymer component B by treating the web or the nonwoven fabric with a group of rolls having a high linear pressure and having a smooth surface, which is not preferable.

Next, the ultrafine long-fiber nonwoven fabric obtained by the method of the present invention will be described.

The ultrafine long-fiber nonwoven fabric obtained by the method of the present invention comprises a polymer component A and two or more segments having a convex lens-like cross section composed of a polymer component B incompatible with the polymer component A. A bicomponent conjugate filament, a bicomponent conjugate filament partially exfoliated from a segment comprising the polymer component B from the bicomponent conjugate filament, and the polymer component developed by splitting the bicomponent conjugate filament. A split fiber composed of only A and a split filament composed of only the polymer component B.

In the ultrafine long-fiber nonwoven fabric of the present invention, the splitting ratio of the segment composed of the polymer component B is 30% or more and 95% or less. The split ratio is defined as a bicomponent conjugate filament in which R ₀ and R ₁ , L ₀ and L ₁ satisfy the above and the formula, and a segment composed of the polymer component B from the bicomponent conjugate filament, which is partially separated. A split bicomponent fiber composed solely of the polymer component A and a split fibrous fiber composed solely of the polymer component B, which are expressed by splitting the bicomponent composite filament. Of the non-woven fabric consisting of 10 parts, taking a cross-sectional photograph by enlarging the cross-section of the non-woven fabric by 100 times, And the total number of existing polymer component B segments are calculated and calculated, and the ratio (%) of the total number of exfoliated polymer component B segments to the total number of existing polymer component B segments is calculated. It represents.

In the ultrafine long-fiber nonwoven fabric of the present invention, the splitting ratio is 30%.
It is preferably at least 95% and the splitting ratio is 30%.
% Is not preferable because a nonwoven fabric having a delicate surface morphology and a dense structure cannot be obtained.

In addition, split filaments composed solely of the polymer component B developed by splitting the composite filaments have a single-fiber fineness.
It is preferably 0.8 denier or less. Even if the splitting ratio is 30% or more, it is difficult to obtain a nonwoven fabric having a delicate surface and a dense structure if the single-filament fineness of the splitting filament made of the polymer component B exceeds 0.8 denier. The smaller the single-fiber fineness, the more a nonwoven fabric having a delicate surface and a dense structure can be obtained.

In the bicomponent bicomponent fiber according to the present invention, the number of segments having a convex lens-shaped cross section composed of the polymer component B is 2
It is necessary to have at least one. If the number of the segments is one, crimping occurs in the conjugate long fiber depending on spinning conditions or drawing conditions, and when the web is formed, the openability of the fiber is reduced and a uniform web cannot be obtained.

In the method of the present invention, various kinds of post-processing conditions such as kinds of polymers to be combined, composite of polymers, spinning conditions, drawing conditions, peeling splitting conditions, bonding conditions, and flexible processing can be selected to achieve the intended purpose. It is possible to produce a corresponding ultrafine long-fiber nonwoven fabric.

(Example) Next, the present invention will be specifically described based on examples.
Various characteristics in the examples were measured by the following methods.

Intrinsic viscosity: Measured at a temperature of 20 ° C using a solution of an equal weight mixture of phenol and ethane tetrachloride as a solution.

Melt index: Measured by ASTM D 1238 E method.

Melting point: Determined from a DSC curve obtained by measuring the amount of a sample at about 5 mg at a scanning rate of 20 ° C./min using a differential scanning calorimeter DSC-2 manufactured by Perkin Elmer.

Tensile strength in the vertical and horizontal directions of the nonwoven fabric: A test specimen having a width of 3 cm and a length of 10 cm was prepared and measured by the stripping method described in JIS L-1096.

Example 1 Composite spinning using a polyethylene polymer having a melting point of 128 ° C. and a melt index value of 80 g / 10 min as a polymer component A, and a polyethylene terephthalate polymer having a melting point of 258 ° C. and an intrinsic viscosity of 0.70 as a polymer component B The bicomponent composite filament was melt-spun through a spinneret having 200 holes. In melt spinning,
Polymer component A has a melting temperature of 230 ° C and a single hole discharge rate of 0.60 g /
The melting temperature of the polymer component B is 285 ° C, and the single hole discharge amount is 0.6
0 g / min (the ratio (weight ratio) of component A to component B is 1 to 1). After cooling the spun long fiber yarn, it is placed under the spinneret.
25 filaments are sucked and drawn through each of eight air satskas arranged at a position of 0 cm, drawn, drawn at a speed of 3100 m / min, and forcibly charged by a charging device to open and move the fibers. The web was obtained by depositing on the web conveyor surface.

As shown in FIG. 3, the cross-sectional shape of the obtained bicomponent composite long fiber is composed of a polymer component A and a segment having six convex lens-shaped cross sections composed of a polymer component B. Was something. Based on the cross-sectional photograph taken by magnifying the fiber cross section by 1000 times, assuming a virtual arc including 90% or more of the six arcs, R ₀ , R ₁ , L _0, and L ₁ are defined. R ₁ / R ₀ and L ₁ / L ₀ were calculated, R ₁ / R ₀ was 0.3, L ₁ / L ₀
Was 1.6. The composite filament was not split, and the web was uniform.

Next, the obtained web was subjected to split and heat bonding twice using a roll group consisting of six rolls of a multi-stage type having a smooth surface and heated to obtain a nonwoven fabric. The processing conditions were as follows: the surface temperature of the heating roll group was 115 ° C., and the linear pressure was 200 kg / cm.

The obtained nonwoven fabric had a basis weight of 50 g / m ² , a tensile strength in the vertical direction of 5.2 kg / 3 cm, and a tensile strength in the horizontal direction of 3.8 kg / 3 cm. Select any 10 places of the nonwoven fabric and set the cross section of the nonwoven fabric to 10
A cross-sectional photograph was taken by magnifying 0 times, and then, in the ten cross-sectional photographs, the total number of segments of the polymer component B and the total number of the existing segments of the polymer component B separated from the composite filament were obtained. When the split ratio was determined, the split ratio was 80%. This nonwoven fabric includes, in addition to split filaments composed only of the polymer component B, bicomponent composite filaments in which the segment composed of the polymer component B is not peeled off at all,
A bicomponent bicomponent fiber in which a segment composed of the polymer component B is partially exfoliated from the bicomponent bicomponent fiber, and a split fiber composed solely of the polymer component A developed by dividing the bicomponent bicomponent fiber. Was observed. The fineness of the split long fiber composed only of the polymer component B developed by splitting the composite long fiber was determined, and was found to be extremely fine, 0.31 denier. The nonwoven fabric had a delicate surface morphology and a dense structure.

Comparative Example 1 Example 1 except that a polyethylene polymer having a melting point of 125 ° C. and a melt index value of 100 g / 10 min was used as the polymer component A.
In the same manner as above, the split type bicomponent composite filament is melt-spun,
After cooling, it is drawn and drawn through a filament through an air filter, taken up at a speed of 3100 m / min, forcibly charged by a charging device to spread the fibers, and deposited on a moving web conveyor surface to obtain a web. Was.

As shown in FIG. 6, the cross-sectional shape of the obtained bicomponent conjugate long fiber was composed of a polymer component A and a segment having six convex lens-shaped cross sections composed of a polymer component B. Was something. Based on the cross-sectional photograph of the fiber cross section, assuming an imaginary arc including 90% or more of the six arcs, R ₀ , R ₁ , L ₀ and L ₁ are obtained, and R ₁ / R ₀ and L ₁ / L ₀
As a result, R ₁ / R ₀ was 0.3 and L ₁ / L ₀ was 3.2. The composite filament was not split, and the web was uniform.

Next, in the same manner as in Example 1, the obtained web was subjected to splitting and heat bonding twice using a group of heated flat rolls to obtain a nonwoven fabric.

The obtained nonwoven fabric had an extremely low splitting ratio of 11%, and did not have a delicate surface morphology and a dense structure.

Example 2 Composite spinning using a polyethylene polymer having a melting point of 128 ° C. and a melt index value of 80 g / 10 min as a polymer component A, and a polyethylene terephthalate polymer having a melting point of 258 ° C. and an intrinsic viscosity of 0.70 as a polymer component B The bicomponent composite filament was melt-spun through a spinneret having 625 holes. In melt spinning,
Polymer component A has a melting temperature of 230 ° C and a single hole discharge rate of 0.20 g /
The melting temperature of the polymer component B is 285 ° C and the single hole discharge rate is 0.2
0 g / min (the ratio (weight ratio) of component A to component B is 1 to 1). After cooling the spun filament yarn, the surface temperature becomes 75
The film was drawn at a speed of 250 m / min by a heating roller group at a temperature of 250 ° C., and stretched at a magnification of 4.0 between the heating roller group and the heating roller group having a surface temperature of 90 ° C. The drawn fiber yarns were suctioned by passing through 25 filaments through 25 air-suckers, forcibly charged by a charging device to spread the fibers, and deposited on a moving web conveyor surface to obtain a web.

The cross-sectional shape of the obtained bicomponent composite filament was as shown in FIG. The fiber cross section based on a cross-section photograph taken magnified 1000 times, was determined the R ₁ / R ₀ and _{L 1 / L 0, R 1} / R 0 is 0.3, L ₁ / L ₀ 1.7 met Was. The composite filament was not split, and the web was uniform.

Next, the obtained web was subjected to split and heat bonding twice using a roll group consisting of six rolls of a multi-stage type having a smooth surface and heated to obtain a nonwoven fabric. The processing conditions were such that the surface temperature of the heating roll group was 115 ° C. and the linear pressure was 200 kg / cm.

The obtained nonwoven fabric had a basis weight of 50 g / m ² , a tensile strength in the vertical direction of 7.0 kg / 3 cm, and a tensile strength in the horizontal direction of 5.2 kg / 3 cm. Select any 10 places of the nonwoven fabric and set the cross section of the nonwoven fabric to 10
A cross section photograph was taken at a magnification of 0 times, and the split fiber ratio was determined. The split fiber ratio was 90%. As in Example 1, in addition to the split filaments composed only of the polymer component B, the nonwoven fabric includes a bicomponent bicomponent fiber in which the segment composed of the polymer component B is not peeled off at all. A split length composed solely of the bicomponent conjugate long fiber in which a segment composed of the polymer component B is partially removed from the bicomponent conjugate long fiber, and the polymer component A developed by dividing the bicomponent conjugate long fiber Fiber was observed. The fineness of the split long fiber composed only of the polymer component B was determined to be 0.23 denier, which was extremely fine. This nonwoven fabric had a delicate surface morphology and a dense structure.

Comparative Example 2 A polyethylene polymer having a melting point of 132 ° C. and a melt index value of 40 g / 10 minutes was polymer component A, and its melting temperature was 232 ° C.
In the same manner as in Example 2, the two-component composite filament was melt-spun and cooled, then taken up by a heating roller group at a speed of 250 m / min, stretched, suctioned through an air sack through a filament, and charged. The fibers are forcibly charged by the device to open the fibers, and are deposited on the moving web conveyor surface.
I got the web.

During stretching, the composite filaments were separated and split on the stretching roller, and the split filaments were wound around the stretching roller. And the obtained web was poor in uniformity.

The cross-sectional shape of the obtained bicomponent composite filament was as shown in FIG. The fiber cross section based on a cross-section photograph taken magnified 1000 times, was determined the R ₁ / R ₀ and _{L 1 / L 0, R 1} / R 0 is 1.2, L ₁ / L ₀ 0.8 met Was. The composite filament was not split, and the web was uniform.

Next, in the same manner as in Example 2, the obtained web was subjected to splitting and heat bonding twice using a heated group of rolls having a smooth surface to obtain a nonwoven fabric.

The obtained non-woven fabric had a high splitting ratio of 95% and had a delicate surface morphology, but was inferior in uniformity and had spots on the basis.

Example 3 The nonwoven fabric obtained in Example 2 was subjected to an embossing treatment using a heated embossing roll. This processing condition is
The surface temperature of the heated embossing roll is 120 ° C and the linear pressure is 30kg /
cm.

The obtained nonwoven fabric has a basis weight of 55 g / m ² , a tensile strength in the vertical direction of 10.7 kg / 3 cm, and a tensile strength in the horizontal direction of 7.9 kg / 3 cm.
It had a delicate surface morphology and a dense structure.

Comparative Example 3 Heated smooth surface 1 was applied to the web obtained in Example 1.
Splitting and heat bonding were performed twice using a pair of rolls.
The processing conditions were as follows: the surface temperature of the heating roll pair was 115 ° C, and the linear pressure was 10 kg / cm.

The nonwoven fabric obtained had an extremely low splitting ratio of 5.3%, and did not have a delicate surface morphology and a dense structure.

(Effect of the Invention) According to the method for producing a nonwoven fabric of ultrafine long fibers of the present invention, it is composed of bicomponent conjugate filaments and split filaments developed by dividing the bicomponent conjugate filaments, and has excellent strength. A nonwoven fabric having extremely high uniformity and a delicate surface morphology and a dense structure can be efficiently manufactured at low cost.

And the obtained nonwoven fabric can be suitably used as a material for a bag or an envelope.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining the structure of a bicomponent conjugate filament according to the present invention. FIGS. 2, 3, 4 and 5 are examples of bicomponent conjugate filaments satisfying the constitutional requirements of the present invention. FIGS. 6 and 7 show cross-sections not satisfying the requirements of the present invention.
It is a cross-sectional view which shows the example of a component composite long fiber.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) D04H 1/00-18/00

Claims (2)

(57) [Claims] 1. A polymer component A, which is incompatible with the polymer component A and has a melting point of from 30 to 150 ° C. from the melting point of the polymer component A.
And a segment having at least two convex lens-shaped cross-sections made of a polymer component B having a high melting point and a radius of curvature R ₀ at a convex lens-shaped portion of the polymer component B in a cross-section perpendicular to the fiber axis. R ₁ , melt composite spinning of bicomponent conjugate filaments having arc lengths L ₀ and L ₁ satisfying the following and formulas, and the spun bicomponent conjugate filaments are taken up by a take-up means comprising an air sucker. , A web composed of a high melting point polymer component B is deposited on a collecting surface of a web conveyor or the like to form a web, and the web is treated with a high linear pressure roll group consisting of two or more rolls. A method for producing a nonwoven fabric of ultrafine long-fiber non-woven fabric, comprising separating at least part of the long fiber from the long fiber into split-split fiber, and at least partially bonding the fibers with the fiber comprising the polymer component A having a low melting point. R ₁ / R ₀ <1 ... 1 <L ₁ / L ₀ ≤3 ... [R ₀ : radius of curvature of an arc not in contact with polymer component A, R ₁ :
Radius of curvature of an arc in contact with polymer component A, L ₀ : arc length of an arc not in contact with polymer component A, L ₁ : arc length of an arc in contact with polymer component A] 2. A split fiber composed solely of a high-melting polymer component B developed by splitting a bicomponent composite filament,
2. The method for producing a nonwoven fabric of ultrafine long fibers according to claim 1, wherein the nonwoven fabric is ultrafine fibers having a single yarn fineness of 0.8 denier or less.